In cardiac patient care and treatment, there is a need to measure cardiac hemodynamic parameters such as blood volumes, blood flow, blood pressure etc. In order to adapt cardiac therapy, continuous information on hemodynamic status is generally necessary. This is true for both parameter optimization of implantable medical devices (IMDs), such as pacemakers, defibrillators and cardioverters, and drug therapy optimization. For patients having an IMD, these measurements often involve highly advanced sensors with complex design including specialized implantable medical leads with miniaturized electronics and sensors in the tip of the implantable medical lead. There is, though, a need for a simple solution to assess and predict the hemodynamic status of patients without the requirements of having specialized equipment and dedicated sensors implanted in the patient's body.
US 2009/0264716 discloses an IMD that classifies a detected tachyarrhythmia as being ventricular tachycardia (VT) or non-VT tachyarrhythmia based on a hemodynamic signal representative of mechanical function of the cardiovascular system. The classification is based on comparing morphological features of the sensed hemodynamic signal to a template and determining a measure of morphological variability.
U.S. Pat. No. 7,062,326 discloses an IMD that determines a ventricular impedance signal and derives a parameter from the impedance signal. This parameter correlates closely to the physical workload and at the same time provides hemodynamic feedback information.
US 2007/0142866 discloses an IMD that records hemodynamic signals, derives parameters from the hemodynamic signals during normal rate and stores the parameters as reference template. When a tachyarrhythmia episode is detected based on the heart rate, the hemodynamic signals are anew recorded, the parameters are extracted therefrom and compared to the reference template. The comparison is employed to determine whether and/or when to deliver anti-tachycardia pacing.
US 2010/0030086 discloses an IMD that monitors intracardiac impedance to determine a change in hemodynamic status of a patient by detecting changes in impedance parameters over heart cycles. The determined impedance parameters are compared to previously determined values and are employed to detect any change in hemodynamic status.
There is still a need for an efficient and patient-specific technique to enable assessment of hemodynamic status in a reliable way.